RDFa was first proposed by Mark Birbeck in the form of a W3C note entitled XHTML and RDF,[3] which was then presented to the Semantic Web Interest Group[4] at the W3C's 2004 Technical Plenary.[3] Later that year the work became part of the sixth public Working Draft of XHTML 2.0.[5][6] Although it is generally assumed that RDFa was originally intended only for XHTML 2, in fact the purpose of RDFa was always to provide a way to add a metadata to any XML-based language. Indeed, one of the earliest documents bearing the RDF/A Syntax name has the sub-title A collection of attributes for layering RDF on XML languages.[7] The document was written by Mark Birbeck and Steven Pemberton, and was made available for discussion on October 11, 2004.

In April 2007 the XHTML 2 Working Group produced a module to support RDF annotation within the XHTML 1 family.[8] As an example, it included an extended version of XHTML 1.1 dubbed XHTML+RDFa 1.0. Although described as not representing an intended direction in terms of a formal markup language from the W3C, limited use of the XHTML+RDFa 1.0 DTD did subsequently appear on the public Web.[9]

October 2007 saw the first public Working Draft of a document entitled RDFa in XHTML: Syntax and Processing.[10] This superseded and expanded upon the April draft; it contained rules for creating an RDFa parser, as well as guidelines for organizations wishing to make practical use of the technology.

RDFa 1.1 reached recommendation status in June 2012.[12] It differs from RDFa 1.0 in that it no longer relies on the XML-specific namespace mechanism. Therefore, it is possible to use RDFa 1.1 with non-XML document types such as HTML 4 or HTML 5. Details can be found in an appendix to HTML 5.[13]

An additional RDFa Primer document was last updated in June 2012.[14] (The first public Working Draft dates back to March 2006.)

RDFa was defined in 2008 with the "RDFa in XHTML: Syntax and Processing" Recommendation.[15] Its first application was to be a module of XHTML.

The HTML applications remained, "a collection of attributes and processing rules for extending XHTML to support RDF" expanded to HTML5, are now expressed in a specialized standard, the "HTML+RDFa" (the last is "HTML+RDFa 1.1 - Support for RDFa in HTML4 and HTML5"[16]).

The "HTML+RDFa" syntax of 2008 was also termed "RDFa 1.0", so, there are no "RDFa Core 1.0" standard. In general this 2008's RDFa 1.0 is used with the old XHTML standards (as long as RDFa 1.1 is used with XHTML5 and HTML5).

Is a W3C Recommendation (1.0 and 1.1) since 2009,[18] as "a minimal subset of RDFa, the Resource Description Framework in attributes, consisting of a few attributes that may be used to express machine-readable data in Web documents like HTML, SVG, and XML. While it is not a complete solution for advanced data markup tasks, it does work for most day-to-day needs and can be learned by most Web authors in a day".[19]

In 2009 the W3C was positioned[20] to retain RDFa Lite as unique and definitive standard alternative to Microdata.[21] The position was confirmed with the publication of the HTML5 Recommendation in 2014.

2013 survey pizza charts of percentual usage,[24] showing that 79% of URLs and 43% of domains use HTML+RDFa. The average 61% (the other 39% was Microformats) is the usage indicator.

The simplified approaches to semantically annotate information items in webpages were greatly encouraged by the HTML+RDFa (released in 2008) and Microformats (since ~2005) standards.

As of 2013[update] these standards was encoding events, contact informations, products, and so on. Despite the vCard semanctis (only basic items of person and organization annotations) dominance,[24] and some cloning of annotations along the same domain, the counting of webpages (URLs) and domains with annotations is an important statistical indicator for usage of semantically annotated information in the Web.

The statistics of 2013 show that usage[24] of HTML+RDFa has passed the usage of Microformats (illustration), consolidating a trend of growth shown in comparisons with 2011 and 2012.

There are already a few RDFa editors available online. RDFaCE (RDFa Content Editor) is a WYSIWYM editor based on TinyMCE to support RDFa content authoring. It supports manual and semi-automatic generation of RDFa with the support of annotation services such as DBpedia Spotlight, OpenCalais, Alchemy API, among others.[25] RDFaCE-Lite is a version of RDFaCE also supporting Microdata and available as a WordPress plugin.[26]

Desktop RDFa editors

AutôMeta is an environment for semi-automatic (or automatic) annotation of documents for publishing on the Web using RDFa. It also includes a RDFa extraction tool to provide the user with a view of the annotated triples. It is available in both CLI and GUI interfaces.[27]

Moreover, RDFa allows the passages and words within a text to be associated with semantic markup:

<pxmlns:dc="http://purl.org/dc/elements/1.1/"about="http://www.example.com/books/wikinomics">
In his latest book
<citeproperty="dc:title">Wikinomics</cite>,
<spanproperty="dc:creator">Don Tapscott</span>
explains deep changes in technology,
demographics and business.
The book is due to be published in
<spanproperty="dc:date"content="2006-10-01">October 2006</span>.
</p>

The following is an example of a complete XHTML+RDFa 1.0 document. It uses Dublin Core and FOAF, an ontology for describing people and their relationships with other people and things:

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML+RDFa 1.0//EN" "http://www.w3.org/MarkUp/DTD/xhtml-rdfa-1.dtd"><htmlxmlns="http://www.w3.org/1999/xhtml"xmlns:foaf="http://xmlns.com/foaf/0.1/"xmlns:dc="http://purl.org/dc/elements/1.1/"version="XHTML+RDFa 1.0"xml:lang="en"><head><title>John's Home Page</title><basehref="http://example.org/john-d/"/><metaproperty="dc:creator"content="Jonathan Doe"/><linkrel="foaf:primaryTopic"href="http://example.org/john-d/#me"/></head><bodyabout="http://example.org/john-d/#me"><h1>John's Home Page</h1><p>My name is <spanproperty="foaf:nick">John D</span> and I like
<ahref="http://www.neubauten.org/"rel="foaf:interest"xml:lang="de">Einstürzende Neubauten</a>.
</p><p>
My <spanrel="foaf:interest"resource="urn:ISBN:0752820907">favorite
book is the inspiring <spanabout="urn:ISBN:0752820907"><citeproperty="dc:title">Weaving the Web</cite> by
<spanproperty="dc:creator">Tim Berners-Lee</span></span></span>.
</p></body></html>

In the example above, the document URI can be seen as representing an HTML document, but the document URI plus the "#me" string http://example.org/john-d/#me represents the actual person, as distinct from a document about them. The foaf:primaryTopic in the header tells us a URI of the person the document is about. The foaf:nick property (in the first span element) contains a nickname for this person, and the dc:creator property (in the meta element) tells us who created the document. The hyperlink to the Einstürzende Neubauten website contains rel="foaf:interest", suggesting that John Doe is interested in this band. The URI of their website is a resource.

The foaf:interest inside the second p element is referring to a book by ISBN number. The resource attribute defines a resource in a similar way to the href attribute, but without defining a hyperlink. Further into the paragraph, a span element containing an about attribute defines the book as another resource to specify metadata about. The book title and author are defined within the contents of this tag using the dc:title and dc:creator properties.

Here are the same triples when the above document is automatically converted to RDF/XML:

<htmlprefix="dc: http://purl.org/dc/elements/1.1/"lang="en"><head><title>John's Home Page</title><linkrel="profile"href="http://www.w3.org/1999/xhtml/vocab"/><basehref="http://example.org/john-d/"/><metaproperty="dc:creator"content="Jonathan Doe"/><linkrel="foaf:primaryTopic"href="http://example.org/john-d/#me"/></head><bodyabout="http://example.org/john-d/#me"><h1>John's Home Page</h1><p>My name is <spanproperty="foaf:nick">John D</span> and I like
<ahref="http://www.neubauten.org/"rel="foaf:interest"lang="de">Einstürzende Neubauten</a>.
</p><p>
My <spanrel="foaf:interest"resource="urn:ISBN:0752820907">favorite
book is the inspiring <spanabout="urn:ISBN:0752820907"><citeproperty="dc:title">Weaving the Web</cite> by
<spanproperty="dc:creator">Tim Berners-Lee</span></span></span>.
</p></body></html>

Note how the prefix foaf is still used without declaration. RDFa 1.1 automatically includes prefixes for popular vocabularies such as FOAF.[29]